Liquid crystal display device and electronic device

ABSTRACT

An active matrix liquid crystal display device including a counter substrate and an element substrate firmly attached with each other with a sealant, and a liquid crystal layer between the counter substrate and the element substrate is provided. The counter substrate is provided with at least a resin layer. An outer end portion of the resin layer is not exposed to the outside atmosphere. The resin layer and the sealant at least partly overlap with each other when seen from a cross section of the liquid crystal display device. A moisture impermeable layer is formed between the resin layer and the sealant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an object, a method, or a manufacturingmethod. Further, the present invention relates to a process, a machine,manufacture, or a composition of matter. In particular, the presentinvention relates to, for example, a semiconductor device, a displaydevice, a light-emitting device, a driving method thereof, or amanufacturing method thereof. In particular, the present inventionrelates to, for example, a liquid crystal display device and anelectronic device using the liquid crystal display device.

2. Description of the Related Art

Liquid crystal display devices for mobile use such as smartphones andtablets are in their heyday. It is reported that despite slow down insales of home-use televisions and the like, some liquid crystal deviceshave been sold well such that demand outstrips supply. There is alwaysreplacement demand for mobile devices usually replaced in a few years,which is different from the case of home-use televisions, and thus themobile devices are lifelines of Japanese display industry in a slump.

Development of highly refined goods is essential to create thereplacement demand; accordingly, displays with high image quality andreduced frame width have been demanded.

A liquid crystal display device has a structure in which a liquidcrystal material is sealed in a space between a pair of substrates whoseperiphery is firmly attached with a sealant. In general, one of the pairof substrates is provided with a color filter and a black matrix, andthe other thereof is provided with a driving element in the case of anactive matrix liquid crystal display device.

In order to prevent moisture absorption and water penetration due toexposure of a planarization film on an element substrate side to theoutside atmosphere, Patent Document 1 discloses a structure in which aplanarization film is provided so that an end portion thereof overlapswith a sealant.

There has been growing demand to reduce a non-display area positionedoutside an effective display area, i.e., the width of a frame area, in aliquid crystal display device. A large-size display with a frame widthof several millimeters and even a small-size display with a frame widthof less than 1 mm have been released.

Although being used for sealing or needed for mounting of a driver, theframe area is greatly reduced due to a reduction in the width.

A sealant used for sealing is a resin and thus has low moisturepermeability but does not completely shield against water.Conventionally, a certain width can be used for a sealing region; thus,influence of water from the outside atmosphere can be reduced at leastfor a period in which a device is driven.

In these days, since a reduction in a frame width is underway, it isdifficult to secure a sufficient frame width.

REFERENCE Patent Document

-   [Patent Document 1] Japanese Patent No. 3531048

SUMMARY OF THE INVENTION

In view of the above, an object of one embodiment of the presentinvention is to provide a highly durable liquid crystal display device.

Another object of one embodiment of the present invention is to providea highly durable liquid crystal display device with a reduced framewidth. Another object of one embodiment of the present invention is toprovide a liquid crystal display device which hardly allows penetrationof water. Another object of one embodiment of the present invention isto provide a liquid crystal display device with a reduced frame width.Another object of one embodiment of the present invention is to providea novel liquid crystal display device. Note that the descriptions ofthese objects do not disturb the existence of other objects. In oneembodiment of the present invention, there is no need to achieve all theobjects. Other objects will be apparent from and can be derived from thedescription of the specification, the drawings, the claims, and thelike.

One embodiment of the present invention is an active matrix liquidcrystal display device including a counter substrate and an elementsubstrate firmly attached with each other with a sealant, and a liquidcrystal layer between the counter substrate and the element substrate.The counter substrate is provided with at least a resin layer. An endportion of the resin layer is not exposed to the outside atmosphere. Theresin layer and the sealant at least partly overlap with each other whenseen from a cross section of the liquid crystal display device. Amoisture impermeable layer is formed between the resin layer and thesealant.

The liquid crystal display device of one embodiment of the presentinvention is a highly durable liquid crystal display device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1F each illustrate a sealing structure.

FIGS. 2A to 2E each illustrate an electrode structure of a liquidcrystal element.

FIGS. 3A to 3E each illustrate a sealing structure.

FIGS. 4A and 4B illustrate a liquid crystal element.

FIGS. 5A and 5B illustrate a liquid crystal display panel (liquidcrystal display module).

FIGS. 6A to 6D illustrate electronic devices.

FIGS. 7A to 7C illustrate an electronic device.

FIGS. 8A and 8B show results of an ESD test (voltage application on acounter substrate side).

FIGS. 9A and 9B show results of an ESD test (voltage application on anelement substrate side).

FIGS. 10A and 10B each illustrate a sealing structure.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below in detail.Note that the present invention is not limited to the description below,and a variety of changes can be made without departing from the spiritand scope of the present invention. Therefore, the present invention isnot construed as being limited to the description given below.

Note that a liquid crystal display device in this specification includesa panel in which a display element is sealed and a module in which anintegrated circuit (IC) or the like including a controller is mounted tothe panel in its category. An element substrate, which corresponds toone embodiment before a display element is completed in a manufacturingprocess of the liquid crystal display device, is provided with means forsupplying current to the display element in each of a plurality ofpixels. Specifically, the element substrate may be in a state in whichonly a pixel electrode of the display element is provided, a state aftera conductive film to be a pixel electrode is formed and before theconductive film is etched to form the pixel electrode, or any of otherstates.

Further, the liquid crystal display device in this specification refersto an image display device or a light source (including a lightingdevice) in some cases. Furthermore, the liquid crystal display devicemay include the following modules in its category in some cases: amodule to which a connector, for example, a flexible printed circuit(FPC) or a tape carrier package (TCP) is attached; a module in which aprinted wiring board is provided at a tip of a TCP; and a module inwhich an IC is directly mounted on a display element by a chip on glass(COG) method.

As a resin used for a planarization film or the like of a liquid crystalelement, acrylic is often used because of its transparency andhandiness. Alternatively, polyimide, a benzocyclobutene-based resin,polyamide, epoxy, or the like can be used. In addition to such organicmaterials, a low-dielectric constant material (a low-k material), asiloxane-based resin, phosphosilicate glass (PSG), borophosphosilicateglass (BPSG), or the like can be used. Such materials are generallyknown to have high moisture permeability. For this reason, a structurein which an end portion of a resin layer such as a planarization film isnot exposed to the outside atmosphere and is positioned in a regionsurrounded by a sealant or inside a sealant is proposed in PatentDocument 1, for example.

A sealant has moisture permeability much lower than those of theabove-described resins that are generally used. A liquid crystal displaydevice with a sufficient frame width can be prevented from beingaffected by water for a long period by using a sealant with a sufficientwidth. However, a liquid crystal display device with a reduced framewidth is easily affected by water because a sealant cannot have asufficient width.

For this reason, it is preferable that a sealant be provided to overlapwith at least part of a resin layer, such as a planarization film or ablack matrix continuously provided also in an effective pixel portion,when seen in the cross section and be formed so that the width of aportion bonded with the sealant is large. Note that the cross section insuch a case is a cross section taken perpendicularly to a displaysurface.

Embodiment 1

FIGS. 1A to 1F are cross-sectional views each illustrating a sealingportion of a liquid crystal display device in this embodiment. In eachof FIGS. 1A to 1F, the right side corresponds to an end portion of theliquid crystal display device and the left side corresponds to an innerside of the liquid crystal display device.

In each of FIGS. 1A to 1F, a counter substrate 100 and an elementsubstrate 101 are firmly attached to each other with a sealant 107, anda liquid crystal layer 102 is provided in a space between the elementsubstrate 101 and the counter substrate 100. The counter substrate 100is provided with color filters 103, a black matrix 104, and aplanarization film 105 covering the color filters 103 and the blackmatrix 104. At least the planarization film 105 is formed of a resin.The material of the planarization film 105 is mainly acrylic or the likeand has moisture permeability more than or equal to 10 times as high asthat of the sealant 107. The black matrix 104 can be formed of a metalor a resin. In the case of using a resin, the black matrix 104 easilytransmits water like the planarization film 105. Note that in the casewhere the black matrix 104 is formed of a resin, the black matrix 104and the planarization film 105 which are formed in contact with eachother as illustrated in FIG. 1A can be regarded as one resin layer.Although not illustrated, an alignment film may be formed in contactwith the liquid crystal layer 102.

In addition, although not illustrated, a driving element, aplanarization film, an alignment film, and the like may be formed overthe element substrate 101, and the element substrate including suchcomponents is referred to as the element substrate 101 here. Note thatthe components of the element substrate 101 are not limited to the abovecomponents, and it is not necessary to form all the components. Forexample, in the case of a passive matrix liquid crystal display device,it is not necessary to form the driving element, and in the case of adisplay mode which does not require the alignment film, such as adisplay mode using a blue phase, it is not necessary to form thealignment film.

FIG. 1A illustrates a structure in which part of a resin layer isexposed to the outside atmosphere. In such a case, the planarizationfilm 105 and the color filters 103 are collectively referred to as theresin layer. In the case where the black matrix 104 is formed of aresin, the black matrix 104, the planarization film 105, and the colorfilters 103 are collectively referred to as the resin layer.

Since part of the resin layer is exposed to the outside atmosphere inthe structure in FIG. 1A, water diffuses into the resin layer relativelyquickly. The water that reaches the liquid crystal layer and the drivingelement might accelerate deterioration of the liquid crystal displaydevice.

For this reason, in the structure in FIG. 1A, a moisture impermeablelayer 106 is provided so that the liquid crystal layer 102 is not incontact with the resin layer. With the moisture impermeable layer 106,water which enters the inside of the resin layer can be inhibited fromreaching the liquid crystal layer and the driving element, which makesit possible to inhibit the deterioration of the liquid crystal displaydevice. Here, the moisture impermeable layer is a layer formed of amaterial having low moisture permeability than a material used for thesealant, and the moisture impermeability thereof is preferably as highas possible.

Note that the moisture permeability of the sealant 107 is approximatelyone-tenth of that of the resin layer; thus, by forming the sealant 107to overlap with the resin layer, a sufficient frame width can be securedeven in a liquid crystal display device with a reduced frame width, andsufficient moisture impermeability can be ensured in normal use.

Further, a reference numeral 108 in the drawing denotes an electrode ofthe liquid crystal display device that is formed of a transparentconductive film. The electrode 108 is not formed in some cases dependingon a driving mode of a liquid crystal, and in such a case, the effect ofthe structure in FIG. 1A that is one embodiment of the present inventionis further exhibited. Examples of the driving mode of such a liquidcrystal display device in which the counter substrate 100 is notprovided with a common electrode are an in-plane switching (IPS) modeand a fringe field switching mode (FFS), for which the structure in FIG.1A can be preferably employed.

In the case where the counter substrate 100 is provided with theelectrode 108, e.g., the case of a multi-domain vertical alignment (MVA)mode in which the electrode 108 is patterned or the case of a twistednematic (TN) mode in which the electrode is formed on the entire surfaceof the substrate, water easily moves from the resin layer to the liquidcrystal layer 102 and the driving element as long as a cut line or ahole is provided in the electrode 108 for the purpose of alignmentcontrol in addition to gassing; therefore, the structure in FIG. 1A canbe preferably employed.

In a structure in FIG. 1B, part of a resin layer is exposed to theoutside atmosphere, which is similar to the structure in FIG. 1A. FIG.1B illustrates the structure in which the black matrix 104 is a resin.

In the resin layer, the planarization film 105 is formed so that anouter end portion thereof is on an inner side than an end portion of theliquid crystal display device and is covered with the sealant 107, andthe black matrix 104 is formed to extend to the end portion of theliquid crystal display device.

In the liquid crystal display device with such a structure, waterrelatively quickly diffuses into the black matrix 104 exposed to theoutside atmosphere and the color filters 103 in contact with the blackmatrix 104. On the other hand, water reaches the planarization film 105slowly compared with that reaches the black matrix 104, the colorfilters 103, or the like because the outer end portion of theplanarization film 105 is covered with the sealant 107. However, in thecase of the planarization film 105 in contact with the black matrix 104and the color filters 103, water diffuses into the planarization film105 from the portion where the planarization film 105 is in contact withthe black matrix 104 and the color filters 103; therefore, it is notworth forming the planarization film 105 so that the outer end portionthereof is on the inner side.

Thus, in the structure in FIG. 1B, the moisture impermeable layer 106 isprovided between a first resin layer (the black matrix 104 and the colorfilters 103) which is exposed to the outside atmosphere and a secondresin layer (the planarization film 105) which is not exposed to theoutside atmosphere.

In this structure, water quickly diffuses into only the first resinlayer, leading to inhibition of the deterioration of the liquid crystaldisplay device.

Here, although having moisture permeability lower than or equal toone-tenth of that of acrylic or the like used for the planarization film105 or the black matrix 104, the sealant 107 is not completelyimpermeable to water. For this reason, even when an outer end portion ofthe planarization film 105 is covered with the sealant 107 and thesealant 107 has a sufficient width, water might enter the planarizationfilm 105 if there is a portion where the sealant 107 and theplanarization film 105 are in contact with and overlap with each other.Once water enters the planarization film 105, the water quicklydiffuses; consequently, an effect of inhibiting entry of water, whichresults from the width of a portion sealed with the sealant 107, cannotbe obtained in some cases.

For example, in the case where the outer end portion of theplanarization film is positioned at the center of the width of thesealant having moisture permeability one-tenth of that of theplanarization film, water that reaches the planarization film at thecenter enters the inside of the liquid crystal display device in abouthalf the time it takes for water to enter the inside of the liquidcrystal display device through the sealant.

For this reason, a moisture impermeable layer is preferably formed in aportion where the planarization film 105 and the sealant 107 overlapwith each other. By forming the moisture impermeable layer between theplanarization film 105 and the sealant 107, a path through which waterenters the planarization film 105 from the sealant 107 is blocked; thus,an effect of inhibiting entry of water, which results from the width ofa portion sealed with the sealant 107, can be obtained as designed.

In the structure in FIG. 1B, the electrode 108 provided under thecounter substrate 100 is also used as a moisture impermeable layer 109.In such a case, the electrode 108 and the moisture impermeable layer 109can be formed in the same step, which is advantageous in terms of cost.Further, in such a structure, a transparent conductor of inorganic oxidewith low moisture permeability or the like, such as transparentconductive oxide, is preferably used for the electrode 108. It isneedless to say that the moisture impermeable layer 109 and theelectrode 108 may be provided in different steps. Note that the moistureimpermeable layer 109 is provided at least in a portion where thesealant 107 and the planarization film 105 overlap with each other.

In a structure in FIG. 1C, the state of water diffusion is differentbetween the case of using a resin for the black matrix 104 and the caseof using a metal for the black matrix 104. In the case of using a resinfor the black matrix 104, part of a resin layer (the color filters 103,the black matrix 104, and the planarization film 105) is exposed to theoutside atmosphere. Hence, the moisture impermeable layer 106 is formedbetween the liquid crystal layer 102 and the resin layer to inhibitwater from entering the liquid crystal layer 102 or the driving element.Further, an outer end portion of the planarization film 105 is formed onan inner side than end portions of the substrates, and a surface of theplanarization film 105 is covered with the sealant 107. Furthermore, theplanarization film 105 and the sealant 107 overlap with each other butare not in direct contact with each other, and the moisture impermeablelayer 106 is formed therebetween; thus, entry of water from the sealant107 to the planarization film 105 is inhibited, which makes it possibleto obtain an effect of inhibiting entry of water, which results from thewidth of a portion sealed with the sealant 107.

In the case of using a metal for the black matrix 104, the resin layer(the color filters 103 and the planarization film 105) is isolated fromthe outside atmosphere even when the moisture impermeable layer 106 isnot formed. Thus, it is less likely to be affected by external water andis possible to inhibit deterioration more effectively. Further, theplanarization film 105 and the sealant 107 overlap with each other butare not in direct contact with each other, and the moisture impermeablelayer 106 is formed therebetween; thus, entry of water from the sealant107 to the planarization film 105 is inhibited, which makes it possibleto obtain an effect of inhibiting entry of water, which results from thewidth of a portion sealed with the sealant 107. Note that in thisstructure, the moisture impermeable layer 106 is provided at leastbetween the sealant 107 and the planarization film 105.

In the case of using either a resin or a metal for the black matrix 104,it is not necessary to form the electrode 108. When the electrode 108 isnot formed, it is more likely to be affected by water which enters theresin layer, in which case this structure can be more preferablyemployed. Even in the case where the electrode 108 is formed, and theelectrode 108 is provided with a hole, a cut line, or a slit or ispatterned, when a surface on which the electrode 108 is formed (themoisture impermeable layer 106 in FIG. 1C) is in contact with the liquidcrystal layer 102, this structure is also preferably employed for thereason similar to the above. Examples of a driving mode of a liquidcrystal display device in which the electrode 108 is not formed includean FFS mode and an IPS mode, and examples of a driving mode of a liquidcrystal display device in which the electrode 108 is patterned includean MVA mode. Further, a hole, a slit, or a cut line is formed in theelectrode 108 for the purpose of gassing or the like in some cases.

In the liquid crystal display device having any of the structures inFIGS. 1A to 1C, light leakage from a backlight on the periphery of thesubstrate or entry of external light can be inhibited because the blackmatrix 104 is formed to extend to end portions of the substrates of theliquid crystal display device, which makes it possible to provide animage which has high quality and is less likely to be affected by lightleakage and external light even when the liquid crystal display devicehas a narrow frame.

FIG. 1D illustrates a structure in which outer end portions of the blackmatrix 104 and the planarization film 105 which are correctivelyreferred to as a resin layer are on an inner side than end portions ofthe substrates of the liquid crystal display device. In this structure,the sealant 107 is on an outer side than the outer end portions of theblack matrix 104 and the planarization film 105; thus, the black matrix104 and the planarization film 105 are shielded from the outsideatmosphere.

The moisture impermeable layer 106 is formed between the black matrix104 which is the resin layer and the sealant 107 to block entry ofwater. Further, by forming the moisture impermeable layer 109 betweenthe planarization film 105 and the sealant 107 to block entry of water,an effect of inhibiting influence of water, which results from the widthof a portion sealed with the sealant 107, can be obtained. FIG. 1Dillustrates an example of using the same material for the electrode 108and the moisture impermeable layer 109 formed between the planarizationfilm 105 and the sealant 107. With such a structure, the moistureimpermeable layer 109 and the electrode 108 can be formed at the sametime, which results in a reduction in manufacturing steps and thus isadvantageous in terms of cost.

In the case of forming the moisture impermeable layer 109 and theelectrode 108 at the same time as described above, the electrode 108 ispreferably formed using transparent conductive oxide with low moisturepermeability, such as ITO. It is needless to say that the moistureimpermeable layer 109 and the electrode 108 can be formed in differentsteps. In such a case, it is not necessary to use a material with lowmoisture permeability for the material of the electrode 108.

Note that it is not necessary to form the electrode 108. When theelectrode 108 is not formed, it is more likely to be affected by waterwhich enters the resin layer, in which case this structure can be morepreferably employed. Even in the case where the electrode 108 is formed,it is more likely to be affected by water from the resin layer when asurface on which the electrode 108 is formed (the planarization film 105in FIG. 1D) is in contact with the liquid crystal layer 102, e.g., whenthe electrode 108 is provided with a hole, a cut line, or a silt, or theelectrode 108 is patterned; therefore, this structure is preferablyemployed.

Such a structure in which the outer end portion of the black matrix 104is on an inner side than the end portions of the substrates of theliquid crystal display device increases resistance to electrostaticdischarge (ESD), which makes it possible to provide a highly reliableand highly durable liquid crystal display device.

In a structure in FIG. 1E, outer end portions of the black matrix 104and the planarization film 105 which are collectively referred to as aresin layer are on an inner side than end portions of the substrates. Inaddition, the outer end portion of the black matrix 104 is on an innerside than the outer end portion of the planarization film 105. An outerend portion of the sealant 107 is on an outer side of the substratesthan the outer end portion of the planarization film 105, an inner endportion of the sealant 107 is on an inner side of the substrates thanthe outer end portion of the planarization film 105, and theplanarization film 105 and the sealant 107 partly overlap with eachother. Furthermore, in the portion where the planarization film 105 andthe sealant 107 partly overlap with each other, the moisture impermeablelayer 109 is formed to inhibit water from entering the resin layer fromthe sealant 107.

In the liquid crystal display device with such a structure, the sealant107 with relatively low moisture permeability is positioned outside theresin layer with relatively high moisture permeability, which makes itpossible to inhibit entry of water. Further, in such a structure, themoisture impermeable layer 109 positioned between the sealant 107 andthe resin layer inhibits water from entering the resin layer from thesealant 107; thus, an effect of inhibiting entry of water, which resultsfrom the width of a portion sealed with the sealant 107, is easilyobtained.

Such a structure in which the outer end portion of the black matrix 104is on an inner side than the end portions of the substrates of theliquid crystal display device increases resistance to ESD, which makesit possible to provide a highly reliable and highly durable liquidcrystal display device.

FIG. 1E illustrates the case where the moisture impermeable layer 109and the electrode 108 formed under the counter substrate 100 are formedin the same step. Such formation of the electrode 108 and the moistureimpermeable layer 109 in the same step leads to a reduction in cost,which has an advantage over the case where the moisture impermeablelayer 109 and the electrode 108 are formed in different steps. Note thatin such a case, transparent conductive oxide with low moisturepermeability is preferably used as the material of the electrode 108.

The electrode 108 and the moisture impermeable layer 109 may be formedin different steps. In such a case, any material can be used for themoisture impermeable layer 109 as long as the material has low moisturepermeability; it is sufficient that the electrode 108 is a transparentconductive film, and it is not necessary to use a material with lowmoisture permeability for the electrode 108.

Note that it is not necessary to form the electrode 108. When theelectrode 108 is not formed, it is more likely to be affected by waterwhich enters the resin layer, in which case this structure can be morepreferably employed. Even in the case where the electrode 108 is formed,it is more likely to be affected by water which enters the resin layerwhen a surface on which the electrode 108 is formed (the planarizationfilm 105 in FIG. 1E) is in contact with the liquid crystal layer 102,e.g., when the electrode 108 is provided with a hole, a cut line, or asilt, or the electrode 108 is patterned; therefore, this structure ispreferably employed.

Such a structure in which the outer end portion of the black matrix 104is on an inner side than the end portions of the substrates of theliquid crystal display device increases resistance to ESD, which makesit possible to provide a highly reliable and highly durable liquidcrystal display device.

Note that the outer end portion of the black matrix on an inner sidethan the end portions of the substrates of the liquid crystal displaydevice contributes to an increase in resistance to ESD; therefore, evenwhen the liquid crystal display device has either of structures in FIGS.10A and 10B, resistance to ESD is increased.

A structure in FIG. 1F is almost similar to that in FIG. 1E; in thestructure in FIG. 1F, an outer end portion of the moisture impermeablelayer 109 is formed on an inner side than end portions of thesubstrates, and the sealant 107 is in contact with the counter substrate100. With the structure in which the sealant 107 is in contact with thecounter substrate 100, a more favorable sealing effect can be obtained,which is preferable.

In the liquid crystal display device with any of the structures in FIGS.1D to 1F, since the black matrix 104 is formed not to extend to the endportions of the substrates, inconvenience caused by light leakage from abacklight or entry of external light might occur. For this reason, inthe liquid crystal display device having any of the structures, thesealant 107 is preferably colored in deep color. Coloring can beperformed by mixing or dispersing a pigment or powder in deep color intothe sealant 107.

FIGS. 2A to 2E are schematic diagrams illustrating arrangement ofelectrodes in liquid crystal display devices for respective drivingmethods. FIGS. 2A to 2E illustrate a counter substrate 150, an elementsubstrate 151, a liquid crystal layer 152, an electrode 158 on thecounter substrate side, an electrode 160 on the element substrate side,and the like. Note that although the element substrate 101 and theelectrode on the element substrate are collectively illustrated as theelement substrate 101 in FIGS. 1A to 1F, the element substrate 151 andthe electrode 160 on the element substrate side are separatelyillustrated in FIGS. 2A to 2E. Although not illustrated, an alignmentfilm may be formed between the electrode 158 and the liquid crystallayer 152 or between the electrode 160 and the liquid crystal layer 152.In FIGS. 1A to 1F, the substrate provided with the resin layer and thelike is illustrated as the counter substrate 100; on the other hand, inFIGS. 2A to 2E, a resin layer, a moisture impermeable layer, and thecounter substrate are collectively illustrated as the counter substrate150.

FIG. 2A is the schematic diagram of arrangement of electrodes in thecase of a twisted nematic (TN) mode or a vertical alignment (VA) mode.Although the electrode 158 on the counter substrate side is notpatterned, a hole, a cut line, a slit, or the like might be formed onthe purpose of gassing or the like; in such a case, any of thestructures described in this embodiment can be preferably employed. Itis needless to say that even when a hole or the like is not formedintentionally, the use of any of the structures described in thisembodiment enables a highly durable liquid crystal display device.

FIG. 2B is the schematic diagram of arrangement of electrodes in thecase of a multi-domain vertical alignment (MVA) mode. The electrode 158on the counter substrate side is patterned, and the liquid crystal layer152 is in contact with a surface on which the electrode 158 is formed.For a liquid crystal display device of this mode having such astructure, any of the structures described in this embodiment can bepreferably employed.

FIG. 2C is the schematic diagram of arrangement of electrodes in thecase of an in-plane switching (IPS) mode. In this display mode, theelectrode 158 on the counter substrate side is not formed, and a liquidcrystal is driven by a horizontal electric field generated between theelectrode 160 on the element substrate 151 side and the electrode 161which is also on the element substrate 151 side. In the liquid crystaldisplay device of this mode having such a structure, an effect ofblocking entry of water cannot be expected from the electrode 158 on thecounter substrate 150 side; therefore, any of the structures describedin this embodiment can be highly preferably employed.

FIG. 2D is the schematic diagram of arrangement of electrodes in thecase of a fringe field switching (FFS) mode. In this display mode, theelectrode 158 on the counter substrate side is not formed, and a liquidcrystal is driven by a fringe electric field formed by providing theelectrode 160 on the element substrate 151 side and providing theelectrode 161 which is also on the element substrate 151 side over theelectrode 160 with an insulating film 162 provided therebetween. In theliquid crystal display device of this mode having such a structure, aneffect of blocking entry of water cannot be expected from the electrode158 on the counter substrate 150 side; therefore, any of the structuresdescribed in this embodiment can be highly preferably employed.

FIG. 2E is the schematic diagram of arrangement of electrodes in thecase of an advanced super view (ASV) mode. In this display mode, theelectrode 158 on the counter substrate 150 side is patterned; thus, anyof the structures described in this embodiment can be preferablyemployed.

FIGS. 3A to 3E each illustrate part of one embodiment of the presentinvention in the IPS mode, the FFS mode, or the like; in FIGS. 3A to 3E,the electrode 158 on the counter substrate 150 side is not formed as inFIGS. 2C and 2D. Note that in FIGS. 3A to 3E, a driving element,electrodes on the element substrate side (the electrodes 160 and 161 inFIGS. 2A to 2E), an alignment film, and the like are collectivelyillustrated as the element substrate 101. Over the element substrate101, the electrodes 160 and 161 appropriate for a display mode areformed.

FIG. 3A corresponds to FIG. 1A. The moisture impermeable layer 106 isformed between a resin layer (the color filters 103, the black matrix104, and the planarization film 105) exposed to the outside atmosphereand the liquid crystal layer 102. This makes it possible to inhibitwater from entering the liquid crystal layer 102 from the resin layerand to reduce an adverse effect due to water. In addition, by formingthe moisture impermeable layer 106 between the sealant 107 and the resinlayer, capability of the sealant 107 and sealing capability expectedfrom the width of a portion sealed with the sealant 107 can be surelyobtained.

FIG. 3B corresponds to FIG. 1B. In a structure in FIG. 3B, the moistureimpermeable layer 106 is formed between a resin layer (the color filters103 and the black matrix 104) exposed to the outside atmosphere and aresin layer (the planarization film 105) whose outer end portion isclose to the liquid crystal layer 102 than the resin layer and isprovided on an inner side than end portions of the substrates and whichis not exposed to the outside atmosphere. With such a structure,although water diffuses relatively quickly into the resin layer exposedto the outside atmosphere, water can be inhibited from entering theplanarization film 105 which is more close to the liquid crystal layer;thus, the liquid crystal layer 102 and the driving element can beinhibited from being adversely affected by water.

Further, the outer end portion of the planarization film 105 is coveredwith the sealant 107; in a portion where at least the planarization film105 and the sealant 107 overlap with each other, the moistureimpermeable layer 109 is formed between the planarization film 105 andthe sealant 107. With such a structure, water can be inhibited fromentering the planarization film 105 from the sealant 107, which makes itpossible to obtain sealing capability expected from the moisturepermeability of the sealant 107 and the width of a portion sealed withthe sealant 107. Although the moisture impermeable layer 109 is providedonly in a portion where the sealant 107 and the planarization film 105substantially overlap with each other in FIG. 3B, the moistureimpermeable layer 109 may be formed on the entire surface of thesubstrate. When the moisture impermeable layer 109 is formed on theentire surface, steps of patterning, etching, and the like are notneeded, resulting in simplification of the manufacturing process. On theother hand, by removing the moisture impermeable layer 109 in aneffective display area as illustrated in FIG. 3B, deterioration ofdisplay quality due to the refractive index, coloring, or the like ofthe moisture impermeable layer 109 can be reduced.

FIG. 3C corresponds to FIG. 1C. In a structure in FIG. 3C, part (onlythe black matrix 104) of a resin layer (the color filters 103, the blackmatrix 104, and the planarization film 105) is exposed to the outsideatmosphere. An outer end portion of the planarization film 105 is on aninner side than the outer peripheries of the substrates; the moistureimpermeable layer 106 is formed between the resin layer and the liquidcrystal layer 102 and between the resin layer and the sealant 107. Sinceonly the black matrix 104 is exposed to the outside atmosphere in theresin layer, the amount of water entering from the outside atmospherecan be minimized. Further, the black matrix 104 which is formed toextend to end portions of the substrates makes it possible to inhibitdecrease in display quality caused by light leakage of a backlight orentry of external light.

FIG. 3D corresponds to FIG. 1D. In a structure in FIG. 3D, an outer endportion of a resin layer (the color filters 103, the black matrix 104,and the planarization film 105) is on an inner side than the outerperipheries of the substrates, and the sealant 107 is on an outer sidethan the outer end portion of the resin layer; thus, the resin layer isnot exposed to the outside atmosphere, resulting in a structure that isless likely to be affected by water. Further, the moisture impermeablelayer 106 is formed at least in a portion where the resin layer and thesealant 107 overlap with each other to inhibit an adverse effect ofwater which enters the resin layer from the sealant 107. Note thatalthough the moisture impermeable layer 106 is provided only in aportion where the sealant 107 and the resin layer substantially overlapwith each other, the moisture impermeable layer 106 may be formed on theentire surface of the substrate. When the moisture impermeable layer 106is formed on the entire surface, steps of patterning, etching, and thelike are not needed, resulting in simplification of the manufacturingprocess. On the other hand, by removing the moisture impermeable layer106 in an effective display area as illustrated in FIG. 3D,deterioration of display quality due to a difference in the refractiveindexes, coloring, or the like of the moisture impermeable layer 106 canbe reduced.

Although the moisture impermeable layer 106 is formed to cover both anouter end portion of the planarization film 105 and an outer end portionof the black matrix 104 after the planarization film 105 is formed, amoisture impermeable layer covering the outer end portion of the blackmatrix 104 and a moisture impermeable layer covering the outer endportion of the planarization film 105 may be formed independently.

Further, since the black matrix 104 is formed not extend to end portionsof the substrates in the structure in FIG. 3D, display quality might bedecreased due to light leakage from a backlight or entry of externallight in the case of a liquid crystal display device with a reducedframe width. In such a case, by mixing a colorant or a pigment into thesealant 107 to color the sealant 107 in deep color, an adverse effectcaused by light leakage or external light can be reduced; thus, thedisplay quality can be maintained.

FIG. 3E corresponds to FIG. 1E. In a structure in FIG. 3E, an outer endportion of a resin layer (the color filters 103, the black matrix 104,and the planarization film 105) is on an inner side than the outerperipheries of the substrates, and the sealant 107 is on an outer sidethan the outer end portion of the resin layer; thus, the resin layer isnot exposed to the outside atmosphere, resulting in a structure that isless likely to be affected by water. Further, the moisture impermeablelayer 106 is formed at least in a portion where the resin layer and thesealant 107 overlap with each other to inhibit an adverse effect ofwater which enters the resin layer from the sealant 107. In thestructure in FIG. 3E, an outer end portion of the black matrix 104 is onan inner side than an outer end portion of the planarization film 105,and thus the black matrix 104 is covered with the planarization film105. Note that although the moisture impermeable layer 106 is providedonly in a portion where the sealant 107 and the resin layersubstantially overlap with each other, the moisture impermeable layer106 may be formed on the entire surface of the substrate. When themoisture impermeable layer 106 is formed on the entire surface, steps ofpatterning, etching, and the like are not needed, resulting insimplification of the manufacturing process. On the other hand, byremoving the moisture impermeable layer 106 in an effective display areaas illustrated in FIG. 3E, deterioration of display quality due to therefractive index, coloring, or the like of the moisture impermeablelayer 106 can be reduced.

Further, since the black matrix 104 is formed not extend to end portionsof the substrates in the structure in FIG. 3E, display quality might bedecreased due to light leakage from a backlight or entry of externallight in the case of a liquid crystal display device with a reducedframe width. In such a case, by mixing a colorant or a pigment into thesealant 107 to color the sealant 107 in deep color, an adverse effectcaused by light leakage or external light can be reduced; thus, thedisplay quality can be maintained.

The structure in any of FIGS. 3D and 3E in which the outer end portionof the black matrix 104 is on an inner side than the end portions of thesubstrates of the liquid crystal display device increases resistance toESD. This makes it possible to provide a highly reliable and highlydurable liquid crystal display device.

With the sealant 107 having a width longer than or equal to 0.2 mm andshorter than or equal to 1.5 mm, preferably longer than or equal to 0.4mm and shorter than or equal to 1 mm, sufficient sealing capability canbe maintained for as long as is needed in a liquid crystal displaydevice with any of the structures described in this embodiment, whilereducing a frame width thereof.

The moisture impermeable layer in this embodiment refers to a materialat least having lower moisture permeability than the sealant; themoisture impermeable layer may have a single-layer structure or astacked-layer structure. Examples of a material preferable for themoisture impermeable layer are silicon nitride, silicon nitride oxide,aluminum nitride, and silicon oxide. Further, the examples can alsoinclude transparent conductive oxide. When the transparent conductiveoxide is used for the moisture impermeable layer, the moistureimpermeable layer and an electrode on the counter substrate side can beformed at the same time, which is preferable. Examples of thetransparent conductive oxide are indium tin oxide (ITO), a conductivematerial in which zinc oxide (ZnO) is mixed with indium oxide, aconductive material in which silicon oxide (SiO₂) is mixed with indiumoxide, organic indium, organotin, indium oxide containing tungstenoxide, indium zinc oxide containing tungsten oxide, indium oxidecontaining titanium oxide, indium tin oxide containing titanium oxide,and graphene; the transparent conductive oxide preferably has a sheetresistance of 10000 Ω/square or less and a light transmittance of 70% orhigher on a wavelength of 550 nm.

The electrode 108, the electrode 160, and the electrode 161 eachcorrespond to a pixel electrode or a common electrode. In the case of atransmissive liquid crystal display device, a pixel electrode layer, acommon electrode layer, an element substrate, a counter substrate, andother components such as an insulating film and a conductive film, whichare provided in a pixel region through which light is transmitted, havea property of transmitting light in the visible wavelength range. In aliquid crystal display device in a mode in which an electric field isapplied in the horizontal direction, such as the IPS mode or the FFSmode, a pixel electrode layer and a common electrode layer preferablyhave a light-transmitting property; however, in the case of a liquidcrystal display device having a structure in which a relatively largeopening pattern is provided, a non-light-transmitting material such as ametal film may be used depending on its shape. Note that in thisspecification, a light-transmitting property refers to a property oftransmitting at least light in the visible wavelength range.

On the other hand, in the case of a reflective liquid crystal displaydevice, a reflective component which reflects light transmitted througha liquid crystal composition (e.g., a reflective film or substrate) maybe provided on the side opposite to the viewing side of the liquidcrystal composition. Therefore, a substrate, an insulating film, and aconductive film, which are provided between the viewing side and thereflective component and through which light is transmitted, have aproperty of transmitting light in the visible wavelength range. In aliquid crystal display device having a structure in which an electricfield is applied in the vertical direction, a pixel electrode layer or acommon electrode layer on the side opposite to the viewing side may havea light-reflecting property so that it can be used as a reflectivecomponent.

The pixel electrode layer and the common electrode layer can be formedusing one or more of the following: indium tin oxide (ITO), a conductivematerial in which zinc oxide (ZnO) is mixed with indium oxide, aconductive material in which silicon oxide (SiO₂) is mixed with indiumoxide, organic indium, organotin, indium oxide containing tungstenoxide, indium zinc oxide containing tungsten oxide, indium oxidecontaining titanium oxide, and indium tin oxide containing titaniumoxide; graphene; metals such as tungsten (W), molybdenum (Mo), zirconium(Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium(Cr), cobalt (Co), nickel (Ni), titanium (Ti), platinum (Pt), aluminum(Al), copper (Cu), and silver (Ag); alloys thereof; and metal nitridesthereof. Further, the pixel electrode layer and the common electrodelayer can be formed using a conductive composition containing aconductive high molecule (also referred to as a conductive polymer). Asthe conductive high molecule, what is called a π-electron conjugatedconductive polymer can be used. For example, polyaniline or a derivativethereof, polypyrrole or a derivative thereof, polythiophene or aderivative thereof, and a copolymer of two or more kinds of them aregiven. The pixel electrode layer and the common electrode layerpreferably have a sheet resistance of 10000 Ω/square or less and a lighttransmittance of 70% or higher on a wavelength of 550 nm. Further, theresistivity of the conductive high molecule contained in the conductivecomposition is preferably 0.1 Ω·cm or less. Materials and structures ofthe electrodes are selected depending on a display mode of the liquidcrystal display device as described above; for example, a material or astructure which transmits or reflects light is selected as appropriate.

As the element substrates 101 and 151 and the counter substrates 100 and150, a glass substrate of barium borosilicate glass, aluminoborosilicateglass, or the like, a quartz substrate, a plastic substrate, or the likecan be used. Note that in the case of the reflective liquid crystaldisplay device, a metal substrate such as an aluminum substrate or astainless steel substrate may be used as a substrate on the sideopposite to the viewing side.

Note that an optical film such as a polarizing plate, a retardationplate, or an anti-reflection film may be provided as appropriate. Inaddition, a backlight or the like can be used as a light source.

The structures, methods, and the like described in this embodiment canbe combined as appropriate with any of the other structures, methods,and the like described in the other embodiments.

Embodiment 2

As the liquid crystal display device of one embodiment of the presentinvention, a passive matrix liquid crystal display device and an activematrix liquid crystal display device can be provided. In thisembodiment, an example of an active matrix liquid crystal display deviceof one embodiment of the present invention is described with referenceto FIGS. 4A and 4B.

FIG. 4A is a plan view of the liquid crystal display device andillustrates two pixels. FIG. 4B is a cross-sectional view taken alongline X1-X2 of FIG. 4A.

In FIG. 4A, a plurality of wirings 405 a are arranged in parallel witheach other (extend in the vertical direction of the drawing) and apartfrom each other. The wirings 405 a serve as source wirings. Wiring layer405 b is formed using a conductive layer which is also used to form thewirings 405 a. A plurality of wirings 401 extend in the directionsubstantially perpendicular to the wirings 405 a (in the horizontaldirection in the drawing) and are arranged apart from each other. Thewirings 401 serve as gate wirings. A first electrode layer 447 isprovided in a substantially rectangular region surrounded by the wirings405 a and the wirings 401. The first electrode layer 447 serves as apixel electrode. In FIG. 4A, a transistor 420 which drives the pixelelectrode is provided in the upper right corner of a substantiallyrectangular region surrounded by the wirings 405 a and the wirings 401.A plurality of pixel electrodes and a plurality of transistors arearranged in matrix.

In the liquid crystal display device in FIGS. 4A and 4B, the firstelectrode layer 447 electrically connected to the transistor 420 througha contact hole 421 serves as the pixel electrode, and a second electrodelayer 446 overlapping with the first electrode layer 447 with aninsulating film 408 provided therebetween serves as a common electrode.A common potential is applied to a common electrode layer.

There is no particular limitation on arrangement of the electrodes, anda method in which a liquid crystal molecule is driven by generating afringe electric field to control gray scale, such as the FFS modeillustrated in FIGS. 3A to 3E, can be used. In addition to such amethod, a driving method using any of the electrode structuresillustrated in FIG. 2A to 2E can be used as appropriate.

As a liquid crystal composition used for a liquid crystal layer, aliquid crystal composition suitable for each driving method can be usedas appropriate.

Having an opening pattern, the second electrode layer 446 is illustratedas divided electrode layers in the cross-sectional view of FIG. 4B. Thesame applies to the other drawings of this specification.

There is no particular limitation on a structure of a transistor whichcan be used for the liquid crystal display device disclosed in thisspecification; for example, a staggered type or a planar type having atop-gate structure or a bottom-gate structure can be used. Further, thetransistor may have a single gate structure including one channelformation region, or a multi gate structure such as a double gatestructure including two channel formation regions or a triple gatestructure including three channel formation regions. Alternatively, thetransistor may have a dual-gate structure including two gate electrodelayers positioned above and below a channel region with a gateinsulating layer provided therebetween.

The transistor 420 illustrated in FIGS. 4A and 4B is an invertedstaggered thin film transistor. The transistor 420 is formed over afirst substrate 441 having an insulating surface, and includes a gateelectrode 401 a, a gate insulating layer 402, a semiconductor layer 403,and the wiring layer 405 b which serves as one of a source electrode anda drain electrode. In addition, an insulating film 407 is stacked tocover the transistor 420. The insulating film 407 may have asingle-layer structure or a stacked-layer structure.

The first substrate 441 and a second substrate (not illustrated) whichis a counter substrate are firmly attached to each other with a sealantwith the liquid crystal layer sandwiched therebetween. A peripheralstructure of the sealant is similar to that described in Embodiment 1.As a method for forming the liquid crystal layer, a dispenser method (adropping method) or an injection method in which a liquid crystalcomposition is injected using capillary action or the like after thefirst substrate 441 is attached to the second substrate can be used.

As the sealant, typically, a visible light curable resin, a UV curableresin, or a thermosetting resin is preferably used. Typically, anacrylic resin, an epoxy resin, an amine resin, or the like can be used.Further, a photopolymerization initiator (typically, an ultravioletlight polymerization initiator), a thermosetting agent, a filler, or acoupling agent may be included in the sealant. In the case where a blackmatrix is formed not to extend to end portions of the substrates, acolorant or a pigment is preferably mixed into the sealant to color thesealant in deep color.

In the case where a photocurable resin such as a UV curable resin isused as the sealant and the liquid crystal composition is formed by adropping method, for example, the sealant may be cured through a lightirradiation step of a polymer stabilization treatment.

In this embodiment, the outside of the first substrate 441 and theoutside of the second substrate (the counter substrate) may be eachprovided with a polarizing plate. In addition to the polarizing plate,an optical film such as a retardation plate or an anti-reflection filmmay be provided. For example, circular polarization by the polarizingplate and the retardation plate may be used. Through the above-describedprocess, a liquid crystal display device can be completed.

In the case of manufacturing a plurality of liquid crystal displaydevices using a large-sized substrate (in the case of a multiple panelmethod), a division step can be performed before the polymerstabilization treatment or before the polarizing plate is provided. Inconsideration of the influence of the division step on the liquidcrystal composition (such as alignment disorder due to force applied inthe division step), it is preferable that the division step be performedafter the first substrate is attached to the second substrate and beforethe polymer stabilization treatment.

Although not illustrated, a backlight, a sidelight, or the like may beused as a light source. Light from the light source is emitted from theside of the first substrate 441 which is an element substrate so as topass through the second substrate on the viewing side.

Any of the materials similar to those of the electrode 108 described inEmbodiment 1 can be used for the first electrode layer 447 and thesecond electrode layer 446. Materials and structures of the electrodelayers are selected depending on a display mode of the liquid crystaldisplay device or a liquid crystal display module as described above;for example, a material or a structure which transmits or reflects lightis selected as appropriate.

An insulating film serving as a base film may be provided between thefirst substrate 441 and the wirings 401. The base film has a function ofpreventing diffusion of an impurity element from the first substrate441, and can be formed to have a single-layer structure or astacked-layer structure using one or more of a silicon nitride film, asilicon oxide film, a silicon nitride oxide film, and a siliconoxynitride film. The wirings 401 can be formed to have a single-layerstructure or a stacked-layer structure using a metal material such asmolybdenum, titanium, chromium, tantalum, tungsten, aluminum, copper,neodymium, or scandium or an alloy material which contains any of thesematerials as its main component. Alternatively, a semiconductor filmtypified by a polycrystalline silicon film doped with an impurityelement such as phosphorus, or a silicide film such as a nickel silicidefilm may be used for the wirings 401. By using a light-blockingconductive film for the wirings 401, light from a backlight (lightemitted through the first substrate 441) can be prevented from enteringthe semiconductor layer 403.

The gate insulating layer 402 can be formed using a silicon oxide film,a gallium oxide film, an aluminum oxide film, a silicon nitride film, asilicon oxynitride film, an aluminum oxynitride film, or a siliconnitride oxide film by a plasma CVD method, a sputtering method, or thelike. Alternatively, a high-k material such as hafnium oxide, yttriumoxide, lanthanum oxide, hafnium silicate, hafnium aluminate, hafniumsilicate to which nitrogen is added, or hafnium aluminate to whichnitrogen is added may be used as a material of the gate insulating layer402. The use of such a high-k material enables a reduction in gateleakage current.

A material of the semiconductor layer 403 is not particularly limitedand may be determined as appropriate in accordance with characteristicsneeded for the transistor 420. Examples of the material which can beused for the semiconductor layer 403 are described.

The semiconductor layer 403 can be formed using the following material:an amorphous semiconductor formed by a sputtering method or avapor-phase growth method using a semiconductor source gas typified bysilane or germane; a polycrystalline semiconductor formed bycrystallizing the amorphous semiconductor with the use of light energyor thermal energy; a microcrystalline semiconductor; or the like. Thesemiconductor layer can be formed by a sputtering method, an LPCVDmethod, a plasma CVD method, or the like.

A typical example of the amorphous semiconductor is hydrogenatedamorphous silicon, and a typical example of a crystalline semiconductoris polysilicon and the like. Polysilicon (polycrystalline silicon)includes high-temperature polysilicon which is formed at processtemperature of 800° C. or higher, low-temperature polysilicon which isformed at process temperature of 600° C. or lower, polysilicon which isformed by crystallizing amorphous silicon with the use of an element orthe like promoting crystallization, and the like. Needless to say, asdescribed above, a microcrystalline semiconductor, or a semiconductorwhich includes a crystalline phase in part of a semiconductor layer canbe used.

Further, the semiconductor layer 403 can be formed using an oxidesemiconductor. As the oxide semiconductor, for example, any of thefollowing can be used: indium oxide; tin oxide; zinc oxide;two-component metal oxides such as an In—Zn-based oxide, a Sn—Zn-basedoxide, an Al—Zn-based oxide, a Zn—Mg-based oxide, a Sn—Mg-based oxide,an In—Mg-based oxide, and an In—Ga-based oxide; three-component metaloxides such as an In—Ga—Zn-based oxide (also referred to as IGZO), anIn—Al—Zn-based oxide, an In—Sn—Zn-based oxide, a Sn—Ga—Zn-based oxide,an Al—Ga—Zn-based oxide, a Sn—Al—Zn-based oxide, an In—Hf—Zn-basedoxide, an In—La—Zn-based oxide, an In—Ce—Zn-based oxide, anIn—Pr—Zn-based oxide, an In—Nd—Zn-based oxide, an In—Sm—Zn-based oxide,an In—Eu—Zn-based oxide, an In—Gd—Zn-based oxide, an In—Tb—Zn-basedoxide, an In—Dy—Zn-based oxide, an In—Ho—Zn-based oxide, anIn—Er—Zn-based oxide, an In—Tm—Zn-based oxide, an In—Yb—Zn-based oxide,and an In—Lu—Zn-based oxide; and four-component metal oxides such as anIn—Sn—Ga—Zn-based oxide, an In—Hf—Ga—Zn-based oxide, anIn—Al—Ga—Zn-based oxide, an In—Sn—Al—Zn-based oxide, anIn—Sn—Hf—Zn-based oxide, and an In—Hf—Al—Zn-based oxide. In addition,any of the above oxide semiconductors may contain an element other thanIn, Ga, Sn, and Zn, for example, SiO₂.

Here, for example, an In—Ga—Zn—O-based oxide semiconductor means anoxide semiconductor containing indium (In), gallium (Ga), and zinc (Zn),and there is no limitation on the composition thereof.

An oxide semiconductor film may be in a non-single-crystal state, forexample. The non-single-crystal state is, for example, structured by atleast one of c-axis aligned crystal (CAAC), polycrystal, microcrystal,and an amorphous part. The density of defect states of an amorphous partis higher than those of microcrystal and CAAC. The density of defectstates of microcrystal is higher than that of CAAC. Note that an oxidesemiconductor including CAAC is referred to as a c-axis alignedcrystalline oxide semiconductor (CAAC-OS).

For example, an oxide semiconductor film may include a CAAC-OS. In theCAAC-OS, for example, c-axes are aligned, and a-axes and/or b-axes arenot macroscopically aligned.

For example, an oxide semiconductor film may include microcrystal. Notethat an oxide semiconductor including microcrystal is referred to as amicrocrystalline oxide semiconductor. A microcrystalline oxidesemiconductor film includes microcrystal (also referred to asnanocrystal) with a size greater than or equal to 1 nm and less than 10nm, for example.

For example, an oxide semiconductor film may include an amorphous part.Note that an oxide semiconductor including an amorphous part is referredto as an amorphous oxide semiconductor. An amorphous oxide semiconductorfilm, for example, has disordered atomic arrangement and no crystallinecomponent. Alternatively, an amorphous oxide semiconductor film is, forexample, absolutely amorphous and has no crystal part.

Note that an oxide semiconductor film may be a mixed film including anyof a CAAC-OS, a microcrystalline oxide semiconductor, and an amorphousoxide semiconductor. The mixed film, for example, includes a region ofan amorphous oxide semiconductor, a region of a microcrystalline oxidesemiconductor, and a region of a CAAC-OS. Further, the mixed film mayhave a stacked structure including a region of an amorphous oxidesemiconductor, a region of a microcrystalline oxide semiconductor, and aregion of a CAAC-OS, for example.

Note that an oxide semiconductor film may be in a single-crystal state,for example.

An oxide semiconductor film preferably includes a plurality of crystalparts. In each of the crystal parts, a c-axis is preferably aligned in adirection parallel to a normal vector of a surface where the oxidesemiconductor film is formed or a normal vector of a surface of theoxide semiconductor film. Note that among crystal parts, the directionsof the a-axis and the b-axis of one crystal part may be different fromthose of another crystal part. An example of such an oxide semiconductorfilm is a CAAC-OS film.

Note that in most cases, a crystal part in the CAAC-OS film fits insidea cube whose one side is less than 100 nm. In an image obtained with atransmission electron microscope (TEM), a boundary between crystal partsin the CAAC-OS film is not clearly detected. Further, with the TEM, agrain boundary in the CAAC-OS film is not clearly found. Thus, in theCAAC-OS film, a reduction in electron mobility due to the grain boundaryis suppressed.

In each of the crystal parts included in the CAAC-OS film, for example,the c-axis is aligned in a direction parallel to a normal vector of asurface where the CAAC-OS film is formed or a normal vector of a surfaceof the CAAC-OS film. Further, in each of the crystal parts, metal atomsare arranged in a triangular or hexagonal configuration when seen fromthe direction perpendicular to the a-b plane, and metal atoms arearranged in a layered manner or metal atoms and oxygen atoms arearranged in a layered manner when seen from the direction perpendicularto the c-axis. Note that among crystal parts, the directions of thea-axis and the b-axis of one crystal part may be different from those ofanother crystal part. In this specification, the term “perpendicular”includes a range from 80° to 100°, preferably from 85° to 95°. Inaddition, the term “parallel” includes a range from −10° to 10°,preferably from −5° to 5°.

In the CAAC-OS film, distribution of crystal parts is not necessarilyuniform. For example, in the formation process of the CAAC-OS film, inthe case where crystal growth occurs from the surface side of the oxidesemiconductor film, the proportion of crystal parts in the vicinity ofthe surface of the oxide semiconductor film is higher than that in thevicinity of the surface where the oxide semiconductor film is formed insome cases. Further, when an impurity is added to the CAAC-OS film,crystallinity of the crystal part in a region to which the impurity isadded is lowered in some cases.

Since the c-axes of the crystal parts included in the CAAC-OS film arealigned in the direction parallel to a normal vector of a surface wherethe CAAC-OS film is formed or a normal vector of a surface of theCAAC-OS film, the directions of the c-axes may be different from eachother depending on the shape of the CAAC-OS film (the cross-sectionalshape of the surface where the CAAC-OS film is formed or thecross-sectional shape of the surface of the CAAC-OS film). Note that thefilm deposition is accompanied with the formation of the crystal partsor followed by the formation of the crystal parts throughcrystallization treatment such as heat treatment. Hence, the c-axes ofthe crystal parts are aligned in the direction parallel to a normalvector of the surface where the CAAC-OS film is formed or a normalvector of the surface of the CAAC-OS film.

With the use of the CAAC-OS film in a transistor, change in electricalcharacteristics of the transistor due to irradiation with visible lightor ultraviolet light is small. Thus, the transistor has highreliability.

The oxide semiconductor layer may have a stacked-layer structure.Description is given of an oxide semiconductor layer having athree-layer structure below; however, the number of stacked layers isnot limited to three.

A first oxide semiconductor layer and a third oxide semiconductor layereach contain one or more of elements included in a second oxidesemiconductor layer. Thus, DOS is less likely to be formed at theinterface between the first oxide semiconductor layer and the secondoxide semiconductor layer and the interface between the second oxidesemiconductor layer and the third oxide semiconductor layer.

An oxide with high carrier mobility may be used for the second oxidesemiconductor layer. An oxide containing indium, a Zn—Sn oxide, or aGa—Sn oxide is preferably used. Further, the second oxide semiconductorlayer preferably contains an element whose bonding energy with oxygen ishigh. Examples of such an element are aluminum, gallium, and yttrium. Anoxide containing such an element can have a large band gap. Furthermore,the second oxide semiconductor layer preferably contains zinc. An oxidecontaining zinc is easily crystallized.

When an In-M-Zn oxide (M is the element whose bonding energy with oxygenis high) is used for the first oxide semiconductor layer, the atomicratio of In to M is preferably as follows: the atomic percentage of Inis lower than 50 atomic % and the atomic percentage of M is higher thanor equal to 50 atomic %, further preferably the atomic percentage of Inis lower than 25 atomic % and the atomic percentage of M is higher thanor equal to 75 atomic %. When an In-M-Zn oxide is used for the secondoxide semiconductor layer, the atomic ratio of In to M is preferably asfollows: the atomic percentage of In is higher than or equal to 25atomic % and the atomic percentage of M is lower than 75 atomic %,further preferably the atomic percentage of In is higher than or equalto 34 atomic % and the atomic percentage of M is lower than 66 atomic %.When an In-M-Zn oxide is used for the third oxide semiconductor layer,the atomic ratio of In to M is preferably as follows: the percentage ofIn is lower than 50 atomic % and the percentage of M is higher than orequal to 50 atomic %, further preferably, the percentage of In is lowerthan 25 atomic % and the percentage of M is higher than or equal to 75atomic %. Note that values of the above atomic ratio of In to Mareobtained when summation of In and M is assumed to be 100 atomic %. Notethat an oxide used for the first oxide semiconductor layer and an oxideused for the third oxide semiconductor layer may have the samecompositions.

In the case of forming the first oxide semiconductor layer by asputtering method, the atomic ratio of a target may be In:M:Zn=1:1:0.5,1:1:1, 1:1:2, 1:3:1, 1:3:2, 1:3:4, 1:3:6, 1:6:2, 1:6:4, 1:6:6, 1:6:8,1:6:10, 1:9:2, 1:9:4, 1:9:6, 1:9:8, or 1:9:10, for example.

In the case of forming the second oxide semiconductor layer by asputtering method, the atomic ratio of a target may be In:M:Zn=3:1:1,3:1:2, 3:1:4, 1:1:0.5, 1:1:1, or 1:1:2, for example.

In the case of forming the third oxide semiconductor layer by asputtering method, the atomic ratio of a target may be In:M:Zn=1:1:0.5,1:1:1, 1:1:2, 1:3:1, 1:3:2, 1:3:4, 1:3:6, 1:6:2, 1:6:4, 1:6:6, 1:6:8,1:6:10, 1:9:2, 1:9:4, 1:9:6, 1:9:8, or 1:9:10, for example.

When any of the semiconductor layers is formed by a sputtering method, afilm whose atomic ratio is slightly different from that of the target isformed in some cases. In particular, the atomic percentage of zinc inthe film becomes smaller than that in the target in some cases.Specifically, the atomic percentage of zinc in the film is higher thanor equal to approximately 40% and lower than or equal to approximately90% of that of zinc in the target in some cases.

In a process of forming the semiconductor layer and the wiring layer, anetching step is employed to process thin films into desired shapes. Dryetching or wet etching can be used for the etching step.

Etching conditions (such as an etchant, etching time, and temperature)are appropriately adjusted depending on a material so that the materialcan be etched into a desired shape.

As a material of the wiring layer 405 b serving as source and drainelectrode layers, an element selected from Al, Cr, Ta, Ti, Mo, and W; analloy containing any of the above elements as its component; an alloyfilm containing a combination of any of the above elements; and the likecan be used. Further, in the case where heat treatment is performed inthe following process, a conductive film with heat resistance againstthe heat treatment is preferably used. For example, since use of Alalone brings disadvantages such as poor resistance to heat and atendency to corrosion, Al is used in combination with a conductivematerial having heat resistance. As the conductive material having heatresistance, which is combined with Al, it is possible to use an elementselected from titanium (Ti), tantalum (Ta), tungsten (W), molybdenum(Mo), chromium (Cr), neodymium (Nd), and scandium (Sc), or nitridecontaining any of these elements as its component, or it is possible touse a stacked-layer structure including Al and any of these elements.

Note that an insulating film may be provided between the wiring layer405 b and the semiconductor layer 403. The insulating film can serve asa channel protective film. The channel protective film may be formedonly over a channel formation region, or may be formed in a region otherthan an opening portion where the wiring layer 405 b and thesemiconductor layer 403 are in contact with each other.

As the insulating film 407 covering the transistor 420, an inorganicinsulating film or an organic insulating film formed by a dry method ora wet method can be used. For example, a silicon nitride film, a siliconoxide film, a silicon oxynitride film, an aluminum oxide film, or atantalum oxide film, which is formed by a CVD method, a sputteringmethod, or the like can be used. Alternatively, an organic material suchas polyimide, acrylic, a benzocyclobutene-based resin, polyamide, orepoxy can be used. Other than such organic materials, it is possible touse a low-dielectric constant material (a low-k material), asiloxane-based resin, phosphosilicate glass (PSG), borophosphosilicateglass (BPSG), or the like. A gallium oxide film may be used as theinsulating film 407.

Note that the insulating film 407 may be formed by stacking a pluralityof insulating films formed using any of these materials. For example,such a structure in which an organic resin film is stacked over aninorganic insulating film may be employed.

By employing a sealing structure of any of the structures described inEmbodiment 1 for a liquid crystal display device or a liquid crystaldisplay module having such a structure, a highly reliable liquid crystaldisplay module or liquid crystal display device can be provided.

The structures, methods, and the like described in this embodiment canbe combined as appropriate with any of the other structures, methods,and the like described in the other embodiments.

Embodiment 3

In this embodiment, an example of a liquid crystal display panel (liquidcrystal display module) with the sealing structure described inEmbodiment 1 is described. In this embodiment, description is given of aliquid crystal display panel (liquid crystal display module) in whichsome or all of driver circuits including transistors and a pixel portionare formed in one substrate; however, it is not limited thereto, and allof the driver circuits may be provided externally or may be formed overone substrate. Although not illustrated, a sensor or a touchscreen maybe provided. For example, an in-cell touch sensor may be built in byusing the second electrode layer 446 or the like serving as a commonelectrode as an electrode for the touch sensor.

The appearance and a cross section of a liquid crystal display panel(liquid crystal display module), which is an embodiment of a liquidcrystal display device, are described with reference to FIGS. 5A and 5B.FIG. 5A is a top view of a panel in which transistors 4010 and 4011formed over a first substrate 4001 and a liquid crystal element 4013 aresealed in a space between the first substrate 4001 and a secondsubstrate 4006 with the use of a sealant 4005. FIG. 5B is across-sectional view taken along the line M-N of FIG. 5A.

The sealant 4005 is provided to surround a pixel portion 4002 and a scanline driver circuit 4004 which are provided over the first substrate4001, and the second substrate 4006 is provided over the pixel portion4002 and the scan line driver circuit 4004. The pixel portion 4002, thescan line driver circuit 4004, and a liquid crystal layer 4008 aresealed in a space between the first substrate 4001 and the secondsubstrate 4006 with the use of the sealant 4005. Outer end portions of ablack matrix 4041, color filters 4040, a planarization film 4042, andthe like are formed on an inner side than end portions of the firstsubstrate 4001 and the second substrate 4006, and the sealant 4005 isformed on an outer side than the outer end portions of the black matrix4041, the color filters 4040, the planarization film 4042, and the like;thus, entry of water through a resin layer is inhibited. In addition, tosecure a sufficient width of a portion sealed with the sealant, part ofthe sealant 4005 overlaps with the resin layer. For this reason, amoisture impermeable layer 4043 is formed between the resin layer andthe sealant 4005 to prevent the loss of sealing capability due to entryof water from the sealant 4005 to the resin layer. Note that thisstructure is an example, and with the use of any of the other sealingstructures described in Embodiment 1, a highly reliable liquid crystaldisplay panel (liquid crystal display module) in which an adverse effectof water is inhibited can be provided.

Note that in the case where an interlayer film 4021 over the firstsubstrate 4001 is also formed using a resin material, a structuresimilar to that of the second substrate 4006 side is employed for thefirst substrate 4001 side; thus, a liquid crystal display module (liquidcrystal display panel) with favorable durability can be provided.

Further, FIG. 5A illustrates the liquid crystal display panel (liquidcrystal display module) in which a signal line circuit formed of asingle crystal semiconductor or a polycrystalline semiconductor isprovided in a region different from a region which is over the firstsubstrate 4001 and is surrounded by the sealant 4005. Note that in FIG.5A, another signal line driver circuit is formed using a transistorprovided over the first substrate 4001. That is, a signal line drivercircuit 4003 a formed using a single crystal semiconductor or apolycrystalline semiconductor is provided, and a signal line drivercircuit 4003 b is mounted over the first substrate 4001.

Note that the connection method of a driver circuit which is separatelyformed is not particularly limited, and a COG method, a wire bondingmethod, a TAB method, or the like can be used. FIG. 5A illustrates anexample where the signal line driver circuit 4003 a is provided by a TABmethod.

The pixel portion 4002 and the scan line driver circuit 4004 providedover the first substrate 4001 include a plurality of transistors. FIG.5B illustrates the transistor 4010 included in the pixel portion 4002and the transistor 4011 included in the scan line driver circuit 4004,as an example. An insulating layer 4020 and the interlayer film 4021 areprovided over the transistors 4010 and 4011.

As the transistors 4010 and 4011, the transistor which is described inEmbodiment 2 can be used.

Further, a conductive layer may be provided over the interlayer film4021 or the insulating layer 4020 so as to overlap with a channelformation region of a semiconductor layer of the transistor 4011 for thedriver circuit. The conductive layer and a gate electrode layer of thetransistor 4011 may have the same potential or different potentials, andthe conductive layer can serve as a second gate electrode layer. Thepotential of the conductive layer may be GND or 0 V, or the conductivelayer may be in a floating state.

A pixel electrode layer 4030 and a common electrode layer 4031 areformed over the interlayer film 4021, and the pixel electrode layer 4030is electrically connected to the transistor 4010. The liquid crystalelement 4013 includes the pixel electrode layer 4030, the commonelectrode layer 4031, and the liquid crystal layer 4008. Note that apolarizing plate 4032 a is provided on the outer side of the firstsubstrate 4001 and a polarizing plate 4032 b is provided on the outerside of the second substrate 4006.

A liquid crystal composition appropriate for a display mode is used forthe liquid crystal layer 4008.

FIGS. 5A and 5B illustrate the liquid crystal display panel (liquidcrystal display module) having a structure in which a liquid crystal ofthe liquid crystal layer 4008 is controlled by generating an electricfield between the pixel electrode layer 4030 and the common electrodelayer 4031 (i.e., the IPS mode). In this structure, an electric field inthe horizontal direction is formed in the liquid crystal, so that liquidcrystal molecules can be controlled using the electric field.

As the first substrate 4001 and the second substrate 4006, glass,plastic, or the like having a light-transmitting property can be used.Examples of the plastic are a fiber reinforced plastic (FRP) plate, apolyvinyl fluoride (PVF) film, a polyester film, and an acrylic resinfilm. Further, a sheet with a structure in which aluminum foil issandwiched between PVF films or polyester films can be used.

Although FIGS. 5A and 5B illustrate an example of a transmissive liquidcrystal display device, one embodiment of the present invention can alsobe used in a semi-transmissive liquid crystal display device or areflective liquid crystal display device.

FIGS. 5A and 5B illustrate the liquid crystal display device in whichthe polarizing plates are provided on the outer side (the view side) ofthe pair of substrates; however, the polarizing plates may be providedon the inner side of the pair of substrates. The position of thepolarizing plates may be determined as appropriate depending on thematerial of the polarizing plates and conditions of the manufacturingprocess. Further, a light-blocking layer serving as a black matrix maybe provided. Furthermore, although not illustrated, the module may beintegrated with a touch panel, or an in-cell touch screen structure maybe further employed.

A color filter layer or a light-blocking layer may be formed as part ofthe interlayer film 4021. In FIGS. 5A and 5B, a light-blocking layer4034 is provided on the second substrate 4006 side to cover thetransistors 4010 and 4011. With the light-blocking layer 4034, thecontrast can be more increased and the transistors can be morestabilized.

The transistors may be covered with the insulating layer 4020 serving asa protective film of the transistors; however, one embodiment of thepresent invention is not particularly limited to such a structure.

Note that the protective film is provided to prevent entry ofcontamination impurities floating in the air, such as an organicsubstance, a metal substance, or moisture, and is preferably a densefilm. The protective film may be formed by a sputtering method to have asingle-layer structure or a stacked-layer structure including any of asilicon oxide film, a silicon nitride film, a silicon oxynitride film, asilicon nitride oxide film, an aluminum oxide film, an aluminum nitridefilm, an aluminum oxynitride film, and an aluminum nitride oxide film.

Furthermore, in the case of further forming a light-transmittinginsulating layer as a planarizing insulating film, thelight-transmitting insulating layer can be formed using an organicmaterial having heat resistance, such as polyimide, acrylic, abenzocyclobutene-based resin, polyamide, or epoxy. Other than suchorganic materials, it is possible to use a low-dielectric constantmaterial (a low-k material), a siloxane-based resin, phosphosilicateglass (PSG), borophosphosilicate glass (BPSG), or the like. Theinsulating layer may be formed by stacking a plurality of insulatingfilms formed using these materials.

Materials similar to those of the pixel electrode layer and the commonelectrode layer described in Embodiment 2 can be used for the pixelelectrode layer 4030 and the common electrode layer 4031. The materialsare selected depending on a display mode of the liquid crystal displaydevice as described above; for example, a material or a structure whichtransmits or reflects light is selected as appropriate.

Furthermore, a variety of signals and potentials are supplied from anFPC 4018 to the signal line driver circuit which is formed separately,the scan line driver circuit 4004, or the pixel portion 4002.

Since the transistor is easily broken due to static electricity or thelike, a protection circuit for protecting the driver circuits ispreferably provided over the same substrate as a gate line or a sourceline. The protection circuit is preferably formed using a nonlinearelement.

In FIGS. 5A and 5B, a connection terminal electrode 4015 is formed usingthe same conductive film as that of the pixel electrode layer 4030, anda terminal electrode 4016 is formed using the same conductive film asthat of source and drain electrode layers of the transistors 4010 and4011.

The connection terminal electrode 4015 is electrically connected to aterminal included in the FPC 4018 through an anisotropic conductive film4019.

Although FIGS. 5A and 5B illustrate an example in which another signalline driver circuit is formed and mounted on the first substrate 4001,one embodiment of the present invention is not limited to thisstructure. Another scan line driver circuit may be formed and mounted,or only some of the signal line driver circuits or some of the scan linedriver circuits may be separately formed and mounted.

In the liquid crystal display panel (liquid crystal display module) withsuch a structure, entry of water from the outside atmosphere can beinhibited; therefore, the liquid crystal display panel (liquid crystaldisplay module) can have high reliability. In addition, the liquidcrystal display panel (liquid crystal display module) can have highdurability.

The structures, methods, and the like described in this embodiment canbe combined as appropriate with any of the other structures, methods,and the like described in the other embodiments.

Embodiment 4

Examples of an electronic device using the above-described liquidcrystal display device are television sets (also referred to astelevisions or television receivers), monitors of computers or the like,digital cameras, digital video cameras, digital photo frames, mobilephone sets (also referred to as mobile phones or mobile phone devices),portable game machines, portable information terminals, audioreproducing devices, and large-sized game machines such as pachinkomachines. Specific examples of these electronic devices are given below.

FIG. 6A illustrates an example of a television set. In the televisionset, a display portion 7103 is incorporated in a housing 7101. Inaddition, here, the housing 7101 is supported by a stand 7105. Thedisplay portion 7103 can display images. The display portion 7103 hasany of the sealing structures described in Embodiment 1. For thisreason, the television set including the display portion 7103 can havehigh durability.

The television set can be operated with an operation switch of thehousing 7101 or a separate remote controller 7110. With an operation pad7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television set is provided with a receiver, a modem, andthe like. With the use of the receiver, general television broadcastingcan be received. Moreover, when the television set is connected to acommunication network with or without wires via the modem, one-way (froma sender to a receiver) or two-way (between a sender and a receiver orbetween receivers) information communication can be performed.

FIG. 6B illustrates a computer including a main body 7201, a housing7202, a display portion 7203, a keyboard 7204, an external connectionport 7205, a pointing device 7206, and the like. Note that in thecomputer, the display portion 7203 has any of the sealing structuresdescribed in Embodiment 1.

FIG. 6C illustrates a portable game machine including two housings, ahousing 7301 and a housing 7302, which are connected with a jointportion 7303 so that the portable game machine can be opened or folded.A display portion 7304 is incorporated in the housing 7301. The displayportion 7304 has any of the sealing structures described inEmbodiment 1. A display portion 7305 is incorporated in the housing7302. In addition, the portable game machine illustrated in FIG. 6Cincludes a speaker portion 7306, a recording medium insertion portion7307, an LED lamp 7308, an input unit (an operation key 7309, aconnection terminal 7310, a sensor 7311 (sensor having a function ofmeasuring force, displacement, position, speed, acceleration, angularvelocity, rotational frequency, distance, light, liquid, magnetism,temperature, chemical substance, sound, time, hardness, electric field,current, voltage, electric power, radiation, flow rate, humidity,gradient, oscillation, odor, or infrared rays), or a microphone 7312),and the like. Needless to say, the structure of the portable gamemachine is not limited to the above as far as a display portion usingthe liquid crystal display device described in Embodiment 1 is used asat least either the display portion 7304 or the display portion 7305, orboth, and the structure can include other accessories as appropriate.The portable game machine in FIG. 6C has a function of reading a programor data stored in a recording medium to display it in the displayportion, and a function of sharing information with another portablegame machine by wireless communication. Note that the functions of theportable game machine in FIG. 6C are not limited to these functions, andthe portable game machine can have various functions. Theabove-described portable game machine including the display portion 7304can have high durability because the display portion 7304 has any of thesealing structures described in Embodiment 1.

FIG. 6D illustrates an example of a mobile phone. The mobile phone isprovided with a display portion 7402 incorporated in a housing 7401,operation buttons 7403, an external connection port 7404, a speaker7405, a microphone 7406, and the like. Note that the display portion7402 included in the mobile phone has any of the sealing structuresdescribed in Embodiment 1. Accordingly, the mobile phone that has thedisplay portion 7402 including the liquid crystal element can have highdurability.

When the display portion 7402 of the mobile phone illustrated in FIG. 6Dis touched with a finger or the like, data can be input to the mobilephone. In this case, operations such as making a call and creating mailcan be performed by touching the display portion 7402 with a finger orthe like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting data such as characters. Thethird mode is a display-and-input mode in which two modes of the displaymode and the input mode are combined.

For example, in the case of making a call or creating mail, a characterinput mode mainly for inputting characters is selected for the displayportion 7402 so that characters displayed on the screen can be input. Inthis case, it is preferable to display a keyboard or number buttons onalmost the entire screen of the display portion 7402.

When a detection device including a sensor for detecting an inclination,such as a gyroscope or an acceleration sensor, is provided inside themobile phone, display on the screen of the display portion 7402 can beautomatically changed by determining the orientation of the mobile phone(whether the mobile phone is placed horizontally or vertically for alandscape mode or a portrait mode).

The screen modes are changed by touch on the display portion 7402 oroperation with the operation buttons 7403 of the housing 7401. Thescreen modes can be switched depending on the kind of images displayedon the display portion 7402. For example, when a signal of an imagedisplayed on the display portion is a signal of moving image data, thescreen mode is switched to the display mode. When the signal is a signalof text data, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed within a specified period while a signal detectedby an optical sensor in the display portion 7402 is detected, the screenmode may be controlled so as to be switched from the input mode to thedisplay mode.

FIGS. 7A and 7B illustrate an example of a foldable tablet terminal. InFIG. 7A, the tablet terminal is unfolded, and includes a housing 9630, adisplay portion 9631 a, a display portion 9631 b, a display-modeswitching button 9034, a power button 9035, a power-saving-modeswitching button 9036, a clip 9033, and an operation button 9038. Notethat in the tablet terminal, one or both of the display portion 9631 aand the display portion 9631 b are formed using a liquid crystal displaydevice with any of the sealing structures described in Embodiment 1.

Part of the display portion 9631 a can be a touchscreen region 9632 aand data can be input when a displayed operation key 9637 is touched.Note that FIG. 7A illustrates, as an example, that half of the area ofthe display portion 9631 a has only a display function and the otherhalf of the area has a touchscreen function. However, the structure ofthe display portion 9631 a is not limited to this, and all the area ofthe display portion 9631 a may have the touchscreen function. Forexample, all the area of the display portion 9631 a can display keyboardbuttons and serve as a touchscreen while the display portion 9631 b canbe used as a display screen.

Like the display portion 9631 a, part of the display portion 9631 b canbe a touchscreen region 9632 b. When a keyboard display switching button9639 displayed on the touchscreen is touched with a finger, a stylus, orthe like, a keyboard can be displayed on the display portion 9631 b.

Touch input can be performed in the touchscreen region 9632 a and thetouchscreen region 9632 b at the same time.

The display-mode switching button 9034 can switch the display betweenportrait mode, landscape mode, and the like, and between monochromedisplay and color display, for example. With the power-saving-modeswitching button 9036, the luminance of display can be optimized inaccordance with the amount of external light at the time when the tabletis in use, which is detected with an optical sensor incorporated in thetablet. The tablet terminal may include another detection device such asa sensor for detecting an inclination (e.g., a gyroscope or anacceleration sensor) in addition to the optical sensor.

Although the display portion 9631 a and the display portion 9631 b havethe same display area in FIG. 7A, one embodiment of the presentinvention is not limited to this example. The display portion 9631 a andthe display portion 9631 b may have different areas or different displayquality. For example, one of the display portions 9631 a and 9631 b maydisplay higher definition images than the other.

FIG. 7B illustrates the tablet terminal which is folded. The tabletterminal includes the housing 9630, a solar cell 9633, a charge anddischarge control circuit 9634, a battery 9635, and a DCDC converter9636. As an example, FIG. 7B illustrates the charge and dischargecontrol circuit 9634 including the battery 9635 and the DCDC converter9636.

Since the tablet terminal is foldable, the housing 9630 can be closedwhen the tablet terminal is not used. As a result, the display portion9631 a and the display portion 9631 b can be protected; thus, a tabletterminal which has excellent durability and excellent reliability interms of long-term use can be provided.

The tablet terminal illustrated in FIGS. 7A and 7B can have otherfunctions such as a function of displaying various kinds of data (e.g.,a still image, a moving image, and a text image), a function ofdisplaying a calendar, a date, the time, or the like on the displayportion, a touch-input function of operating or editing the datadisplayed on the display portion by touch input, and a function ofcontrolling processing by various kinds of software (programs).

The solar cell 9633, which is attached on the surface of the tabletterminal, supplies electric power to a touchscreen, a display portion,an image signal processor, and the like. Note that the solar cell 9633is preferably provided on one or both surfaces of the housing 9630, inwhich case the battery 9635 can be charged efficiently.

The structure and operation of the charge and discharge control circuit9634 illustrated in FIG. 7B are described with reference to a blockdiagram in FIG. 7C. FIG. 7C illustrates the solar cell 9633, the battery9635, the DCDC converter 9636, a converter 9638, switches SW1 to SW3,and the display portion 9631. The battery 9635, the DCDC converter 9636,the converter 9638, and the switches SW1 to SW3 correspond to the chargeand discharge control circuit 9634 in FIG. 7B.

First, an example of operation in the case where power is generated bythe solar cell 9633 using external light is described. The voltage ofpower generated by the solar cell is raised or lowered by the DCDCconverter 9636 so that the power has a voltage for charging the battery9635. Then, when power supplied from the battery 9635 charged by thesolar cell 9633 is used for the operation of the display portion 9631,the switch SW1 is turned on and the voltage of the power is raised orlowered by the converter 9638 so as to be voltage needed for the displayportion 9631. In addition, when display on the display portion 9631 isnot performed, the switch SW1 is turned off and the switch SW2 is turnedon so that the battery 9635 may be charged.

Although the solar cell 9633 is described as an example of a powergeneration means, the power generation means is not particularlylimited, and the battery 9635 may be charged by another power generationmeans such as a piezoelectric element or a thermoelectric conversionelement (Peltier element). The battery 9635 may be charged by anon-contact power transmission module which is capable of charging bytransmitting and receiving power by wireless (without contact), oranother charge means used in combination, and the power generation meansis not necessarily provided.

Needless to say, one embodiment of the present invention is notparticularly limited to the electronic device with the shape illustratedin FIGS. 7A to 7C as long as the display portion 9631 is included.

Example 1

In this example, examination results of an increase in the resistance toESD due to a structure in which an outer end portion of a black matrixis positioned on an inner side than end portions of substrates aredescribed.

In this example, an ESD test was conducted on a liquid crystal displaydevice in which a driver circuit and a pixel portion are formed over onesubstrate to check a change in operation clearance (margin). Theoperation clearance (margin) refers to clearance of a voltage set in adesign specification, and a normal operation can be performed even whena power supply voltage is lowered as long as the voltage is within themargin.

Measured samples are each an active matrix liquid crystal display devicein which a pixel circuit and a driver circuit are formed over a firstsubstrate (element substrate). The driver circuit and the pixel circuitwere each formed using a bottom-gate top-contact semiconductor elementincluding an oxide semiconductor in an active layer. The semiconductorelement was covered with an acrylic resin layer to be planarized, and acommon electrode was formed over the acrylic resin layer. A pixelelectrode was formed over an insulating film (silicon nitride film)which was formed to cover the common electrode, and was covered with analignment film. The liquid crystal display device in this example is aliquid crystal display device of the FFS mode.

A second substrate (counter substrate) was provided with a black matrix,color filters, a planarization film of an acrylic resin also serving asan overcoat layer, and an alignment film, and was sealed with a sealantat the peripheries of the end portions of the substrates.

The ESD test was conducted as follows: a gun type testing machine basedon the IEC standard 61000-4-2 was used, and a positive voltage and anegative voltage were each successively discharged ten times atintervals of 1 second in the condition where discharge resistance was330Ω and discharge capacity was 150 pF. ESD was applied to threeportions in total, that is, around the centers of two scan line drivercircuits provided to face each other with a pixel region providedtherebetween and a portion of the pixel region close to an inputterminal. Results are shown in FIGS. 8A and 8B and FIGS. 9A and 9B.FIGS. 8A and 8B show the results at the time of applying ESD on thecounter substrate side and FIGS. 9A and 9B show the results at the timeof applying ESD on the element substrate side. The graphs in FIG. 8A andFIG. 9A each show results of the display device in which the blackmatrix was formed to extend to the end portions of the substrates. Thegraphs in FIG. 8B and FIG. 9B each show results of the display device inwhich an outer end portion of the black matrix was on an inner side thanthe end portions of the substrates by approximately 180 μm to 290 μm.

In FIG. 8A and FIG. 9A each showing the results of the liquid crystaldisplay device in which the black matrix was formed to extend to the endportions of the substrates, the operation clearance (margin) of adriving element starts to decrease when ESD stress voltage exceeds 6 kV,and the margin is zero at 10 kV, which indicates that the liquid crystaldisplay devices are inoperative. On the other hand, in FIG. 8B and FIG.9B each showing the liquid crystal display device in which the outer endportion of the black matrix was on an inner side than the end portionsof the substrates by approximately 180 μm to 290 μm, the operationclearance (margin) does not decrease even when a 12 kV of ESD isapplied, which suggests that the resistance to ESD is increased in aliquid crystal display device having the structure.

This application is based on Japanese Patent Application serial No.2013-032084 filed with Japan Patent Office on Feb. 21, 2013, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A liquid crystal display device comprising: anelement substrate; a counter substrate facing the element substrate; aliquid crystal layer between the counter substrate and the elementsubstrate; a resin layer on the counter substrate; a planarization filmcovering the resin layer on the counter substrate, the planarizationfilm comprising a resin; an electrode on the planarization film, theelectrode having an opening pattern selected from one or more of a hole,a slit, and a cut line; a sealant between the counter substrate and theelement substrate; and a moisture impermeable layer covering an outerend of the planarization film, wherein the opening pattern of theelectrode does not overlap with the sealant, wherein an outer end of themoisture impermeable layer is provided between the sealant and thecounter substrate, and wherein the outer end of the planarization filmand an outer end of the resin layer are not exposed to an outsideatmosphere.
 2. The liquid crystal display device according to claim 1,wherein the outer end of the moisture impermeable layer is exposed tothe outside atmosphere.
 3. The liquid crystal display device accordingto claim 1, wherein the resin layer includes at least one of a blackmatrix and a color filter.
 4. The liquid crystal display deviceaccording to claim 1, wherein the moisture impermeable layer comprises amaterial selected from the group consisting of silicon nitride, siliconnitride oxide, aluminum nitride, silicon oxide, indium tin oxide, aconductive material in which zinc oxide is mixed with indium oxide, aconductive material in which silicon oxide is mixed with indium oxide,organic indium, organotin, indium oxide containing tungsten oxide,indium zinc oxide containing tungsten oxide, indium oxide containingtitanium oxide, indium tin oxide containing titanium oxide, andgraphene.
 5. The liquid crystal display device according to claim 1,wherein the moisture impermeable layer comprises a transparentconductive oxide.
 6. The liquid crystal display device according toclaim 1, wherein the electrode comprises a transparent conductive oxide.7. The liquid crystal display device according to claim 1, wherein apart of the sealant is in contact with the counter substrate.
 8. Theliquid crystal display device according to claim 1, wherein the liquidcrystal layer is in contact with the electrode.
 9. The liquid crystaldisplay device according to claim 1, wherein a display mode of theliquid crystal display device is an IPS mode or an FFS mode.
 10. Theliquid crystal display device according to claim 1, wherein the elementsubstrate has a transistor including an active layer comprising an oxidesemiconductor.
 11. A liquid crystal display device comprising: anelement substrate; a counter substrate facing the element substrate; aliquid crystal layer between the counter substrate and the elementsubstrate; a resin layer on the counter substrate; a planarization filmcovering the resin layer on the counter substrate, the planarizationfilm comprising a resin; an electrode on the planarization film, theelectrode having an opening pattern selected from one or more of a hole,a slit, and a cut line; a sealant between the counter substrate and theelement substrate; and a moisture impermeable layer covering an outerend of the planarization film, wherein the opening pattern of theelectrode does not overlap with the sealant, wherein the moistureimpermeable layer is provided between the sealant and the planarizationfilm, and wherein the outer end of the planarization film and an outerend of the resin layer are not exposed to an outside atmosphere.
 12. Theliquid crystal display device according to claim 11, wherein an outerend of the moisture impermeable layer is exposed to the outsideatmosphere.
 13. The liquid crystal display device according to claim 11,wherein the resin layer includes at least one of a black matrix and acolor filter.
 14. The liquid crystal display device according to claim11, wherein the moisture impermeable layer comprises a material selectedfrom the group consisting of silicon nitride, silicon nitride oxide,aluminum nitride, silicon oxide, indium tin oxide, a conductive materialin which zinc oxide is mixed with indium oxide, a conductive material inwhich silicon oxide is mixed with indium oxide, organic indium,organotin, indium oxide containing tungsten oxide, indium zinc oxidecontaining tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, and graphene.
 15. The liquidcrystal display device according to claim 11, wherein the moistureimpermeable layer comprises a transparent conductive oxide.
 16. Theliquid crystal display device according to claim 11, wherein theelectrode comprises a transparent conductive oxide.
 17. The liquidcrystal display device according to claim 11, wherein a part of thesealant is in contact with the counter substrate.
 18. The liquid crystaldisplay device according to claim 11, wherein the liquid crystal layeris in contact with the electrode.
 19. The liquid crystal display deviceaccording to claim 11, wherein a display mode of the liquid crystaldisplay device is an IPS mode or an FFS mode.
 20. The liquid crystaldisplay device according to claim 11, wherein the element substrate hasa transistor including an active layer comprising an oxidesemiconductor.
 21. A liquid crystal display device comprising: anelement substrate; a counter substrate facing the element substrate; aliquid crystal layer between the counter substrate and the elementsubstrate; a resin layer on the counter substrate; a planarization filmcovering the resin layer on the counter substrate, the planarizationfilm comprising a resin; an electrode on the planarization film, theelectrode having an opening pattern selected from one or more of a hole,a slit, and a cut line; a sealant between the counter substrate and theelement substrate; and a moisture impermeable layer covering an outerend of the planarization film, wherein the opening pattern of theelectrode does not overlap with the sealant, wherein the moistureimpermeable layer is provided over the sealant and the liquid crystallayer and under the counter substrate, and wherein the outer end of theplanarization film and an outer end of the resin layer are not exposedto an outside atmosphere.
 22. The liquid crystal display deviceaccording to claim 21, wherein an outer end of the moisture impermeablelayer is exposed to the outside atmosphere.
 23. The liquid crystaldisplay device according to claim 21, wherein the resin layer includesat least one of a black matrix and a color filter.
 24. The liquidcrystal display device according to claim 21, wherein the moistureimpermeable layer comprises a material selected from the groupconsisting of silicon nitride, silicon nitride oxide, aluminum nitride,silicon oxide, indium tin oxide, a conductive material in which zincoxide is mixed with indium oxide, a conductive material in which siliconoxide is mixed with indium oxide, organic indium, organotin, indiumoxide containing tungsten oxide, indium zinc oxide containing tungstenoxide, indium oxide containing titanium oxide, indium tin oxidecontaining titanium oxide, and graphene.
 25. The liquid crystal displaydevice according to claim 21, wherein the moisture impermeable layercomprises a transparent conductive oxide.
 26. The liquid crystal displaydevice according to claim 21, wherein the electrode comprises atransparent conductive oxide.
 27. The liquid crystal display deviceaccording to claim 21, wherein a part of the sealant is in contact withthe counter substrate.
 28. The liquid crystal display device accordingto claim 21, wherein the liquid crystal layer is in contact with theelectrode.
 29. The liquid crystal display device according to claim 21,wherein a display mode of the liquid crystal display device is an IPSmode or an FFS mode.
 30. The liquid crystal display device according toclaim 21, wherein the element substrate has a transistor including anactive layer comprising an oxide semiconductor.